Refine offset logic for narrows.
Refine offset logic for narrows.

We now only preserve the offset for the previous
selection (pre-narrow) if that is still the id
we want selected after calling maybe_add_local_messages.

Right not this does not change any behavior, but
upcoming changes to maybe_add_local_messages will
change the selected id to the first unread message
in certain circumstances, in which case preserving
the offset will possibly be confusing, since you're
not on the same message.

tommyip/zulip,eeshangarg/zulip,showell/zulip,tommyip/zulip,andersk/zulip,tommyip/zulip,showell/zulip,synicalsyntax/zulip,rishig/zulip,shubhamdhama/zulip,tommyip/zulip,andersk/zulip,shubhamdhama/zulip,eeshangarg/zulip,punchagan/zulip,jackrzhang/zulip,hackerkid/zulip,andersk/zulip,kou/zulip,brainwane/zulip,showell/zulip,jackrzhang/zulip,punchagan/zulip,rht/zulip,tommyip/zulip,shubhamdhama/zulip,rishig/zulip,jackrzhang/zulip,showell/zulip,zulip/zulip,eeshangarg/zulip,rishig/zulip,eeshangarg/zulip,rht/zulip,zulip/zulip,dhcrzf/zulip,zulip/zulip,timabbott/zulip,punchagan/zulip,kou/zulip,jackrzhang/zulip,shubhamdhama/zulip,timabbott/zulip,brainwane/zulip,rishig/zulip,eeshangarg/zulip,dhcrzf/zulip,synicalsyntax/zulip,tommyip/zulip,brainwane/zulip,jackrzhang/zulip,hackerkid/zulip,timabbott/zulip,dhcrzf/zulip,jackrzhang/zulip,andersk/zulip,jackrzhang/zulip,eeshangarg/zulip,zulip/zulip,showell/zulip,synicalsyntax/zulip,dhcrzf/zulip,andersk/zulip,rishig/zulip,brainwane/zulip,synicalsyntax/zulip,andersk/zulip,timabbott/zulip,brainwane/zulip,andersk/zulip,dhcrzf/zulip,kou/zulip,kou/zulip,kou/zulip,showell/zulip,punchagan/zulip,hackerkid/zulip,shubhamdhama/zulip,synicalsyntax/zulip,punchagan/zulip,synicalsyntax/zulip,rht/zulip,hackerkid/zulip,punchagan/zulip,zulip/zulip,rishig/zulip,rht/zulip,timabbott/zulip,rht/zulip,brainwane/zulip,hackerkid/zulip,punchagan/zulip,timabbott/zulip,rishig/zulip,rht/zulip,kou/zulip,hackerkid/zulip,brainwane/zulip,synicalsyntax/zulip,rht/zulip,shubhamdhama/zulip,tommyip/zulip,dhcrzf/zulip,timabbott/zulip,eeshangarg/zulip,zulip/zulip,hackerkid/zulip,dhcrzf/zulip,shubhamdhama/zulip,showell/zulip,zulip/zulip,kou/zulip